Studied by 0 people
Looks like no one added any tags here yet for you.
Fossil
preserved remains or traces of a once-living organism that lived in the past
Fossil record
history of life documented through fossils
Importance of fossils found in Australia for evidence of megafauna existence
The fossils may be parts of the megafauna, so finding these fossils in australia and dating them will help give evidence for their existence and when they existed.
isotope
Atoms with the same number of protons, same place on the periodic table (the same chemical element), but different number of neutrons
relative atomic mass
average weighted mass of all isotopes of an element
difference between the structure of an isotope and atom
Isotopes have a different mass number due to the different amount of neutrons it has
how the relative mass of an element is calculated
(Mass number of isotope x abundance (%)) + (Mass number of isotope x abundance (%)) = Total Mass number of isotopes/100
radioactive decay
Unstable isotopes that decay/change into another isotope and produce alpha, beta, and/or gamma radiation
radioisotope/radionuclide
An unstable isotope that breaks down
alpha radiation
The nucleus ejects an alpha particle (a). This only occurs to atoms with very heavy nuclei, such as a mass number of over 100.
alpha particle
2 protons, 2 neutrons (aka helium)
charge and speed of alpha radiation (charge, speed)
+2, 10% speed of light
beta radiation
a beta particle leaves the atom, and a neutron in the nucleus decays into a proton
beta particle
electron
charge and speed of beta radiation (charge, speed)
-1, 90% speed of light
gamma radiation
Emission of gamma rays after alpha or beta particle leaves atom when nucleus is still excited
gamma rays
high energy electromagnetic rays. comparable to high energy x-rays
charge and speed of gamma radiation (charge, speed)
0, speed of light
relationship between a half-life and the number of atoms of a substance
when you find the half-life of a radioisotope, half of the atoms in the substance have decayed
examples of radioisotopes
Carbon-14, hydrogen-3, lithium-5
risks associated with radioactivity
When a person comes in skin contact with a radioactive object, the DNA can be damaged in the person’s cells and cause health issues
carbon dating
The dating of organic samples that must contain carbon. It works by measuring the ration of carbon-14 to carbon-12. The less carbon-14, the older the sample.
how the half-life of a radioisotope can be used to ‘tell time
When the half-life is determined, the absolute age of a sample can be found.
how the known half-life of radioisotopes can be used to determine the age of megafauna
By multiplying the half-life by two, you can find out when the decay (death) of the megafauna occurred, therefore find out how long ago they existed
how carbon dating has been used to establish that Aboriginal Peoples have been present on the Australian continent for more than 60,000 years
absolute dating
determines the actual age of a sample in years
relative dating
determines whether a sample is younger or older than another
absolute dating techniques
Carbon dating, potassium-argon dating, uranium-thorium dating, dendrochronology
relative dating techniques
law of superstition, correlation of rock strata, fluorine dating
limitations for carbon-14 dating
Only used on organic samples, must be younger than 60,000 years old
limitations for potassium-40 dating
Only used on samples that contain igneous rock, must be older than 200,000 years old
limitations for uranium-238 dating
Only used on samples that contain sea sediment or coral, must be younger than 600,000 years old
strong nuclear force
Holds protons and neutrons in the nucleus together. The electric force between protons makes them repel each other, however the nuclear force counteracts the electric force, because it is more attractive and stronger in extremely small distances.
